Berlin 2008 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 26: Spin Dynamics / Spin -Torque II
MA 26.8: Vortrag
Donnerstag, 28. Februar 2008, 16:15–16:30, EB 301
Crosstalk of dipolar spin-wave modes in thin Nickel films — •Benjamin Lenk, Marija Djordjevic, Jakob Walowski, Gerrit Eilers, and Markus Münzenberg — IV. Physikalisches Institut, Universität Göttingen
The relaxation mechanisms in thin Nickel films are investigated with all optical pump-probe experiments. Laser pulses with a duration of 60fs from a Ti:Sa mode-coupled laser system are used for optical excitation (pump pulse) as well as observation of the subsequent magnetic relaxation taking place in the pico- and nanosecond regime (probe pulse). The relaxation spectra, i.e. the time dependent magnetization curves M(t), are recorded using the time-resolved magneto-optical Kerr effect (TRMOKE). Numerical analysis yields the relaxation frequencies for all layer thicknesses ranging from 40nm to 220nm on a wedge sample.
Different modes are observed that can be attributed to i) uniform precession of the spins ii) exchange-dominated perpendicular standing spin waves as well as iii) dipole-dominated surface modes. By applying an external field 0mT ≤ µ0H ≤ 150mT dispersion relations ω(H) are determined for the different modes at each layer thickness. The experimental results are compared to theoretical equations derived from the Landau-Lifschitz-Gilbert equation of motion. Good agreement is seen with partly strong deviations at points of mode crossing.
Research is supported by DFG Schwerpunkt SPP 1133: "Ultrafast magnetization processes".